Antimicrobial Activity and Antioxidant Capacity of Thyme, Rosemary and Clove Essential Oils and Their Mixtures

In this study, antimicrobial and antioxidant properties of thyme (Thymus vulgaris L., TEO), rosemary (Rosmarinus officinalis L., REO) and clove essential oils (Syzygium aromaticum L., CEO) and their mixtures (TEO/REO, TEO/CEO, REO/CEO and TEO/REO/CEO) at 1/1 ratio have been evaluated. The agar well diffusion method has been used for screening the antimicrobial activity against Bacillus subtilis, Escherichia coli O157:H7, Listeria monocytogenes and Staphylococcus aureus. For the antioxidant capacity of essential oils and their mixtures, FRAP and DPPH scavenging activity methods have been applied. All of the essential oils and their mixtures have shown an antimicrobial activity against the test microorganisms and an increased antioxidant capacity. TEO has displayed the highest inhibition zones against B. subtilis, E. coli O157:H7, L. monocytogenes and S. aureus. In general, the mixing of TEO with other essential oils has caused a decrease of its antimicrobial activity when compared with TEO alone. The lowest antimicrobial activity has been observed from REO alone and mixing REO with TEO and/or CEO has led to an increase of the antimicrobial activity of REO. The FRAP value of essential oils and their mixtures have ranged from 254.83 to 721.16 mM Fe (II)/mL, while the DPPH scavenging activity values have ranged from 0.155 to 4.121 μL oil. All the essential oils and their mixtures have displayed an antioxidant capacity, however the highest antioxidant capacity have been determined by using CEO in both methods, followed by TEO, and REO has showed the lowest antioxidant capacity. These results support the utilization of essential oils extracted from thyme, rosemary and clove and their mixtures at 1/1 ratio as a natural antimicrobial and antioxidant agent in the food industry.